It has long been known that resistance training can provide functional benefits as well as improve overall health and well-being. For example, resistance training has long been known to improve posture, provide improved support for joints, increase bone density, improve cardiac function, and reduce the risk of injury from everyday activities. As a result, resistance training has often been used in conjunction with other physical activity such as cardiovascular activity.
Aging individuals often have participated in resistance training to assist in prevention of some of the loss of muscle tissue that normally accompanies aging, and to help prevent osteoporosis. For many people in rehabilitation or with an acquired disability, such as those experiencing a stroke or orthopedic surgery, resistance training has often been a central element to a recovery program. The use of resistance machines that operate within an isolated range of motion have aided in the rehabilitation of injuries without aggravating existing injuries or risking new ones.
Common resistance training and rehabilitation programs have included the use of resistance to muscular contraction in order to improve such attributes as strength, anaerobic endurance, muscle size, etc. Resistance-training programs have been customized in order to emphasize improvement of specific physical attributes and conditions.
For example, one common program uses fewer repetitions with relatively higher degrees of resistance. Such a program is often used when strength improvement is desired.
Conversely, another common program has utilized increased repetitions with relatively lower degrees of resistance. Such programs have often been used for muscle toning and for rehabilitation of injuries.
In addition, programs have incorporated combinations in which resistance can be increased or decreased between sets or even between or during repetitions. One common form of increasing and decreasing of resistance is known a “pyramiding,” which increases resistance to a peak level during a series of sets and then decreases the resistance during another series of sets. Another form of varying resistance, called “ramping” or “static training,” increases or decreases resistance near or at the end of a exercise stroke. Yet another variable resistance technique, called “muscle confusion,” involves varying the types of resistance experienced by given muscles between exercise sessions or sets of sessions. Other common weight changing terminology is “weight stripping” (removing weight during or in between exercises) and “weight augmenting” (adding weight during or in between exercises).
To optimize training time and training efficiency, trainers often prepare customized resistance training programs in advance of training an individual. These programs are often hand written or stored on a portable electronic device to be referred to and/or followed during training. While these programs can be shared with a trainee, the trainee may lack the expertise to perform the exercises properly on their own. A professional athlete, for example, may be on an extended trip to locations remote from the trainer. The trainer can send customized training programs to the athlete, but they may not be able to perform the exercises properly, and most often there will be no objective record of how or when training was performed.
Conventional resistance training systems therefore have long included structure for varying the degree of resistance during use. One common type of such system is a gravity weight system. This gravity weight system provides differing weights that can be engaged and disengaged in order to obtain the desired level of resistance.
One problem with the gravity weight system is that the weight of the system increases as the maximum gravity-weight-based resistance provided by the system increases. As a result, gravity weight based systems, particularly those that can provide hundreds of pounds of resistance, are cumbersome, costly and difficult to ship, and difficult to otherwise move, They can also present substantial risk of injury from use of weights and the possibly of mechanical failure of system components.
For example, a gravity weight system presents injury risk due to the inertial mass of the weights in the system. The resulting higher level of force required to overcome the inertia of a given weight or group of weights, and thus initiate movement of the weight(s), can create a risk of excessive strain on the user's muscles and tendons. This risk increases with use of heavier weight(s) in the system, which have greater inertial mass and require greater levels of force to overcome associated inertia and at the same move the weight against the force of gravity.
One solution to the size, weight, and inertial mass presented by gravity weight systems has utilized elastic bands, arms, or springs rather than weights to provide resistance. This type of system, often referred to as an elastometric system, can be much lighter and easier to package, ship, and move. It typically presents much less inertial mass to be moved by the user as well.
One problem with elastometric systems is that the elastic bands, arms, and springs provide limited resistance zones because they can only be stretched or bent so far before they will cease stretching or bending (or even possibly break). This results in a limited maximum stroke length for a particular resistance training movement. Further, elastometric systems present relatively inconsistent and unreliable levels of resistance due to, among other things, diminishing levels of resistance provided by the band, arm, or spring structures as they deteriorate through use and age.
In addition, like weight resistance systems, the number of levels of resistance provided by elastometric systems are typically relatively limited to the relatively few levels of elastometric bands, arms, or spring included in an elastometric system or the number of weights in a weight system. Although the number of resistance levels can be increased in these systems by providing further numbers of bands, arms, or springs, or weights, the size, weight, expense, and difficulty of these systems increases along with the increase in numbers of such components.
Another problem presented by elastometric systems is that they often do not provide, as is often desired, the same level resistance throughout a desired exercise stroke or the ability to reverse the nature of the varying resistance presented to the user. Thus, in elastometric systems in which resistance increases during the first, outgoing stroke (i.e., the positive stroke) and decreased during the reverse, ingoing stroke (the negative stroke), they do not provide the ability to reverse that aspect of their operation and decrease resistance during the positive stroke, and increase it during the negative stroke.
In this regard, differential resistance training varies resistance depending on the direction of the stroke, with the positive stroke usually presenting a lower degree of resistance than that provided during the negative stroke. As explained above, other types of resistance training present significant other variations in resistance levels during repetitions (e.g., ramping), from repetition to repetition, set to set (e.g., pyramiding), and exercise session to exercise session or groups of sessions to session or group of sessions (e.g., muscle confusion).
One method of differential resistance training has utilized a weight based system. Differential resistances are achieved by a partnering assistant who helps lift the weight during the positive stroke and refrains from assisting during the negative stroke. Partnering also been used to also accomplish other weight based, variable resistance exercise formats, such as ramping, pyramiding, muscle confusion, spotting, and others.
One problem with the partnering method is that it requires an additional person to achieve the desired varying resistance. In addition, the partnering method is inefficient and imprecise, as it relies on the partner's sense of what degree of assistance to provide and when to provide it. The partnering method also does not ensure a full range of motion for the person performing the positive and negative stroke due to the partner's exercise of discretion about when to provide or cease providing assistance. Similarly, the partnering method further does not provide the type of rapid yet precise change in resistance that may often be desired, such as with a resistant rapid ramp at the end of an exercise stroke.
One attempt to provide greater reliability and consistency in varying resistance exercise has utilized a hydraulic system or motor to assist or oppose movement of a traditional weight stack. These types of systems, however, still require the use of a weight stack and have the same types of weight, size, and movement problems provided by weight based systems noted above.
Another method of providing variable resistance has utilized a hydraulic mechanism to provide an adjustable resistance level without the use of weighted elements. The hydraulic mechanism typically provides passive resistance, providing resistance only when the user pushes or pulls against linkage connected to a hydraulic cylinder. As a result, such hydraulic systems do not provide forced variable resistance training such as that provided by elastometric systems. They also do not provide any resistance, much less variable resistance, when stroke movement stops, such as at the beginning or end of a stroke. Hydraulic systems usually are also relatively slow in changing resistance levels.
Pneumatic resistance systems have also been developed. Some of these types of systems utilize electronic regulators to supply air cylinders and accumulator tanks with compressed air. The electronic regulator controls pressure and maintains a selected pressure setting by adding or relieving air during each movement or stroke made by the user. These pneumatic systems typically have relatively imprecise structures for determining and setting the resistance level. They also typically have not included mechanisms for forcing differential or other varying resistance levels at varying levels specified by the user; and pneumatic systems are typically slower than hydraulic systems in changing resistance levels.
Further, pneumatic systems typically do not provide resistance similar to that of a weight stack or free weights. The differing pneumatic type of resistance can negatively impact the exercise experience and result in reduced motivation in engaging in or completing an exercise regimen.
Other systems and methods for creating variable resistance include a resistance mechanism that progressively varies resistance applied to a lifting mechanism during the positive stroke, and decreases resistance to substantially zero during the negative strokes. Some of these systems utilize motors or hydraulic forces to either create the resistance or modify or oppose the resistance provided by a traditional weight stack. Such systems have been utilized to provide pyramiding exercise schemes for example. However, these systems lack full adjustability and present issues such as those described above, such as inability to implement other resistance profiles, differing exercise programs, etc.
Some prior systems have use a brake or similar system to create increased resistance on the return stroke of a cable or lever. These systems, however, can produce excess heat, inefficiently use power via thermal losses, and lack precise configurability or programmability due to lack of control in applying the brake instantaneously or consistently as the brake system wears through use.
Yet other systems utilize a motor coupled to a clutch, such as a frictionless eddy-current clutch, or torque converter to provide an adjustable resistance to a load member to oppose a predetermined training movement performed by a user. These systems detect the location and direction of the load member and modify the torque applied to the load member to provide a consistent resistance felt by a user during both a positive and negative stroke. Although these systems can eliminate the need for a bulky weight stack, they utilize power inefficiently by controlling the torque and hence the resistance felt by the user via a clutch, i.e., underutilizing power supplied to the motor. Furthermore, these systems, although allowing for some adjustability of resistance versus the position of the load member, do not provide a precise programmable resistance profile to implement varying other resistance techniques, such as elastometrics, ramping, pyramiding, or muscle confusion.
Other systems have utilized a low voltage DC motor to simulate a weight stack, except that the amount of resistances provided the motor is dependent on the amount of displacement during an exercise stroke. These systems thus provide for a “soft start,” providing lower starting resistance (unlike that inertial mass that must be overcome in a weight based system) to enhance user safety. However, these systems have not themselves provided other types of variable resistance techniques such as ramping, elastometric resistance, pyramiding, or differential resistance.
Other systems provide for adjustability relative to position and relative to resistance, such as constant velocity variable resistance or more traditional variable resistance applications and further provide for customizable resistance profiles. However, these systems do not provide for accurate simulations of elastometric resistance profiles or customize end ramping or forced negative profiles.
Programmable systems utilizing motors or hydraulic forces to emulate pyramiding often lack the ability to combine other exercise profiles with pyramiding, such as, for example, elastomeric pyramiding.